Re: [libvirt] [PATCH 1/2] qemu: support for kvm-hint-dedicated performance hint

From: Wim ten Have <wim.ten.have(a)oracle.com&gt; QEMU version 2.12.1 introduced a performance feature under commit be7773268d98 ("target-i386: add KVM_HINTS_DEDICATED performance hint") This patch adds a new KVM feature 'hint-dedicated' to set this performance hint for KVM guests. The feature is off by default. To enable this hint and have libvirt add "-cpu host,kvm-hint-dedicated=on" to the QEMU command line, the following XML code needs to be added to the guest's domain description in conjunction with CPU mode='host-passthrough'. <features> <kvm> <hint-dedicated state='on'/> </kvm> </features> ... <cpu mode='host-passthrough ... /> Signed-off-by: Wim ten Have <wim.ten.have(a)oracle.com&gt; Signed-off-by: Menno Lageman <menno.lageman(a)oracle.com&gt; --- docs/formatdomain.html.in | 7 +++++++ docs/schemas/domaincommon.rng | 5 +++++ src/conf/domain_conf.c | 4 ++++ src/conf/domain_conf.h | 1 + src/qemu/qemu_command.c | 13 +++++++++++++ 5 files changed, 30 insertions(+) diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in index 6d084d7c0472..c9b18b57e1fc 100644 --- a/docs/formatdomain.html.in +++ b/docs/formatdomain.html.in @@ -2044,6 +2044,7 @@ &lt;/hyperv&gt; &lt;kvm&gt; &lt;hidden state='on'/&gt; + &lt;hint-dedicated state='on'/&gt; &lt;/kvm&gt; &lt;pvspinlock state='on'/&gt; &lt;gic version='2'/&gt; @@ -2217,6 +2218,12 @@ <td>on, off</td> <td><span class="since">1.2.8 (QEMU 2.1.0)</span></td> </tr> + <tr> + <td>hint-dedicated</td> + <td>Set the "dedicated physical CPU" performance hint ("-cpu kvm-hint-dedicated=on")</td>

+ <td>on, off</td> + <td><span class="since">5.7.0 (QEMU 2.12.1)</span></td> + </tr> </table> </dd> <dt><code>pmu</code></dt> diff --git a/docs/schemas/domaincommon.rng b/docs/schemas/domaincommon.rng index a0771da45b5d..08853f9d9e92 100644 --- a/docs/schemas/domaincommon.rng +++ b/docs/schemas/domaincommon.rng @@ -5965,6 +5965,11 @@ <ref name="featurestate"/> </element> </optional> + <optional> + <element name="hint-dedicated"> + <ref name="featurestate"/> + </element> + </optional> </interleave> </element> </define> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c index 03312afaaff8..3907fcf6e5ca 100644 --- a/src/conf/domain_conf.c +++ b/src/conf/domain_conf.c @@ -202,6 +202,7 @@ VIR_ENUM_IMPL(virDomainHyperv, VIR_ENUM_IMPL(virDomainKVM, VIR_DOMAIN_KVM_LAST, "hidden", + "hint-dedicated", ); VIR_ENUM_IMPL(virDomainMsrsUnknown, @@ -20412,6 +20413,7 @@ virDomainDefParseXML(xmlDocPtr xml, switch ((virDomainKVM) feature) { case VIR_DOMAIN_KVM_HIDDEN: + case VIR_DOMAIN_KVM_DEDICATED: if (!(tmp = virXMLPropString(nodes[i], "state"))) { virReportError(VIR_ERR_XML_ERROR, _("missing 'state' attribute for " @@ -22624,6 +22626,7 @@ virDomainDefFeaturesCheckABIStability(virDomainDefPtr src, for (i = 0; i < VIR_DOMAIN_KVM_LAST; i++) { switch ((virDomainKVM) i) { case VIR_DOMAIN_KVM_HIDDEN: + case VIR_DOMAIN_KVM_DEDICATED: if (src->kvm_features[i] != dst->kvm_features[i]) { virReportError(VIR_ERR_CONFIG_UNSUPPORTED, _("State of KVM feature '%s' differs: " @@ -28124,6 +28127,7 @@ virDomainDefFormatFeatures(virBufferPtr buf, for (j = 0; j < VIR_DOMAIN_KVM_LAST; j++) { switch ((virDomainKVM) j) { case VIR_DOMAIN_KVM_HIDDEN: + case VIR_DOMAIN_KVM_DEDICATED: if (def->kvm_features[j]) virBufferAsprintf(&childBuf, "<%s state='%s'/>\n", virDomainKVMTypeToString(j), diff --git a/src/conf/domain_conf.h b/src/conf/domain_conf.h index bce47443c858..f7423b1b6f89 100644 --- a/src/conf/domain_conf.h +++ b/src/conf/domain_conf.h @@ -1765,6 +1765,7 @@ typedef enum { typedef enum { VIR_DOMAIN_KVM_HIDDEN = 0, + VIR_DOMAIN_KVM_DEDICATED, VIR_DOMAIN_KVM_LAST } virDomainKVM; diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c index 71a36ff63a81..ab535af5efb6 100644 --- a/src/qemu/qemu_command.c +++ b/src/qemu/qemu_command.c @@ -7212,6 +7212,19 @@ qemuBuildCpuCommandLine(virCommandPtr cmd, virBufferAddLit(&buf, ",kvm=off"); break; + case VIR_DOMAIN_KVM_DEDICATED: + if (def->kvm_features[i] == VIR_TRISTATE_SWITCH_ON) { + if (def->cpu && def->cpu->mode == VIR_CPU_MODE_HOST_PASSTHROUGH) { + virBufferAddLit(&buf, ",kvm-hint-dedicated=on"); + } else { + virReportError(VIR_ERR_CONFIG_UNSUPPORTED, "%s", + _("kvm-hint-dedicated=on is only applicable when " + "<cpu mode=\"host-passthrough\" .../> is in effect")); + goto cleanup; + } + } + break;